The authorities in Jordan say they have arrested 11 militants alleged to have planned attacks on Western diplomats and shopping centres in the capital.

Government spokesman Samih Maayta said the suspects were arrested in the past few days and were in police custody.

Mr Maayta said the men had brought in weapons from neighbouring Syria, and al-Qaeda operatives in Iraq had helped them manufacture home-made explosives.

The plot was said to have been in preparation since June.

Jordanian intelligence were monitoring the plotters, including their experiments with explosives, a senior official told the BBC's Frank Gardner.

The official told the BBC "this was an al-Qaeda plot timed for the anniversary of the 9 November attacks on Amman in 2005".

Analysis

By Frank GardnerBBC security correspondent

From the details given out by the Jordanian authorities this would appear to be the most serious al-Qaeda plot to target Jordan since the multiple hotel bombings of 2005.

A senior Jordanian official has told the BBC that Jordanian intelligence had the plotters under surveillance from day one. Even so, the plot's international dimensions will alarm diplomats and governments throughout the region.

It seems mortar bombs were being sourced from Syria, technical bomb-making expertise from al-Qaeda operatives in Iraq, and detailed on-the-ground reconnaissance of the targets to hit gathered in the Jordanian capital, Amman. The range of those targets is both ambitious and terrifying, from shopping malls, to embassies, foreign tourists and hotels.

As the plot is analysed in detail it will likely add urgency to calls in the region to resolve the conflict next door in Syria, which is now spilling ever more across its borders.

Jordan border Syria and is home to at least 200,000 Syrians who have fled the conflict, more than any other country in the region.

Elections ahead

The aim of the attack was to "create a highly destructive explosive that would cause the highest number of casualties and extensive physical damage", Petra said.

News of the alleged plot came as the country prepares to vote for a new parliament in January.

Jordan is a key ally of the US in the region.

It has often arrested terror suspects, analysts say.

It has its own militant Salafist movement - ultra-conservatives who want Islamic Sharia law to be implemented in Jordan as a prelude to an Islamic state.

Some members have been convicted of trying to recruit people to fight against US-led troops in Iraq and Afghanistan, plotting attacks against US and Israeli embassies in Amman, or planning to kill foreign tourists.